Nowadays, science education should focus on the development of competences in students, and especially on the development of different skills that allow them to develop their critical thinking (CT), without forgetting the emotional aspects of students that can significantly influence the teaching-learning process. Argumentation and decision making are considered important skills to develop CT and can be developed through socioscientific issues in the classroom. A training programme for pre-service science teachers (PST) on CT was developed based on these ideas, focusing on socioscientific issues in different formats (text, video and opinions). This programme was implemented with 43 Spanish PSTs from the Master in Secondary Education at the University of xx during the academic course 2019-2020. The first phase analysed the emotions felt by the PSTs during the implementation of different issues included in the programme focused on energy, health, or technology. For data collection, the PSTs completed a questionnaire, including a list of emotions. The data were analysed qualitatively, comparing positive and negative emotions. It was found that, regardless of the dilemma format used, the emotions felt by the PSTs were positive, with particular emphasis on their interest and attentiveness. Insecurity appeared in the short opinions´ format to solve the dilemma as a main negative emotion. These results show that the use of socioscientific issues in different formats can be very suitable for developing CT since the emotions detected favour learning.